running test single threaded

Co-authored-by: Michael Bolin <mbolin@openai.com>

codex-rs/core/tests/suite/exec_policy.rs

@@ -20,7 +20,7 @@ use core_test_support::wait_for_event;
 use serde_json::json;
 use std::fs;
 
-#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+#[tokio::test]
 async fn execpolicy_blocks_shell_invocation() -> Result<()> {
     let mut builder = test_codex().with_config(|config| {
         config.features.enable(Feature::ExecPolicy);